Answers

Try calling Dave at 800-564-2987 and see if he has anything to help.

It would need to be sanded back down to good wood. Wear good dust masks.

You could apply Interior Acrylic Topcoat from Perma Chink, but it will have a slight sheen to it. Call Dave at 800-564-2987 for more help. He may have another product that would work for you.

Call Dave at 800-564-2987. He may be able to help with what you need.

Nope, You may want to apply another coat of Shell Guard in 10 years or so.

Sorry, I do not know of anyone.

You should have it corn cob blasted first or the black will just continue to grow under whatever you put on it. Call Mike at 866-670-3020 for help.

You could, but be sure that all rot is taken care of and put a vapor barrier on first.

No. Use a good quality latex stain and topcoat. Call Dave at 800-564-2987 for help with products

1) You can just remove rot from surface and fill. 2) Yes on #2 3) Yes, the paint is probably contributing to the rot issue. 4) I would not caulk the checks unless you know it is letting water get in behind the siding.